1. Field of the Invention
This invention relates to a semiconductor memory device.
2. Description of the Related Art
Most of information processing devices such as conventional workstations and personal computers employ magnetic disk devices as memory devices, respectively. The magnetic disk device has some advantages of high recording reliability and low bit cost, but some disadvantages of large device size and low physical impact resistance.
The magnetic disk device employs the operation principle of conducting magnetic recording of data and magnetic reading out of data for a magnetic recording medium. The movable portions such as the magnetic recording medium and the magnetic head of the magnetic disk device may cause malfunction and failure for the magnetic disk device when physical impact is applied to the magnetic disk device. Moreover, the movable portions of the magnetic disk device pose an impediment for downsizing of the magnetic disk device.
In this point of view, the magnetic disk device does not work against a desktop computer which is to be used under the condition of fixing to a desk, but works against a small and portable laptop computer and notebook computer.
Recently, in this point of view, attention is paid to a small semiconductor memory device with large physical impact resistance. In these latter days when a large capacity memory such as a NAND flash memory is developed, the semiconductor memory device raises expectations for the substitution of the magnetic disk device more than ever.
The semiconductor device is configured such that a plurality of semiconductor memory chips are arranged in parallel on a surface of a wiring board and controller chips for corresponding to the semiconductor memory chips are also arranged in parallel on the same surface of the wiring board. Moreover, some high-speed cache memories as buffer memories for storing data temporally are arranged on the same surface of the wiring board as occasion demands, in addition to the semiconductor chips (Reference 1)
[Reference 1] JP-A 07-078056 (KOKAI)